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Bearing Unit Converter — mm, inch, N, lbf, °C
Convert bore and dimension units, force, torque, pressure and temperature - the units that appear on bearing drawings and data sheets.
Temperature
Units you meet on bearing drawings
Metric catalogue bearings use millimetres and newtons; inch-series bearings - R, RLS, KLNJ, and many aerospace and legacy designs - use inches and pounds. Ratings appear as kN for metric parts and lbf or lb for inch parts, and older drawings may give kgf. Mixing them is the most common arithmetic error in a bearing specification, so convert first and state the unit in the quotation.
Common inch bore equivalents
Fractional inch bores convert to the following metric values, which is how inch bearings are matched to metric shafts:
Temperature: grease life and clearance change with temperature, so convert before comparing a duty with a catalogue rating.
Frequently asked questions
How many mm is a 1/2 inch bore bearing?
12.7 mm. Fractional inch bores are exact multiples of 25.4 mm divided by the denominator, so 1/2″ is 12.7 mm, 5/8″ is 15.875 mm and 3/4″ is 19.05 mm.
Can a metric bearing replace an inch bearing?
Only if the boundary dimensions match after conversion, which they usually do not - inch series follow a different dimension plan. Check bore, outside diameter and width, or use the cross-reference search for the specific number.
Why do older drawings use kgf?
Because the metric technical system used kilogram-force as a unit of force before the newton was adopted. 1 kgf is the force a 1 kg mass exerts under standard gravity - 9.80665 N - so a rating in kgf is about ten times the value in newtons.
Need the exact bearing for this duty?
Send the load, speed and environment - we will suggest the type, clearance and lubricant.